title: Characterization of two families of tandem repeated DNA sequences in Potamogeton pectinatus L.
abstract: DNA sequences belonging to two families of tandem repeats, PpeRsa1 (362-364 bp in length, 62% A+T residues) and PpeRsa2 (355-359 bp in length, 59% A+T residues), have been isolated from the Potamogeton pectinatus L. genome. The two sequence families do not share significant nucleotide sequence similarity, even if an evolutionary relationship between them could be assumed. The comparison of the cleaving activity of isoschizomeres that are either sensitive or insensitive to methylation of cytosine residues in the target sequence revealed high methylation in both sequence families. The copy number per 1C DNA of PpeRsa1- and PpeRsa2-related sequences is estimated to be 4.92 x 10(4) and 7.96 x 10(4), respectively. Taken together, these sequences account for about 7.5% of the entire genome of P. pectinatus. The chromosomal organization of these sequences was investigated by fluorescent in situ hybridization. PpeRsa1 and PpeRsa2 repeats found related sequences in 52 chromosomes of the P. pectinatus complement (2n = 78). The related sequences were localized around the centromeres and at the chromosome ends in three pairs of chromosomes, while they were found only at the chromosome ends in the remaining pairs. Twenty-six chromosomes did not show any hybridization signal. The hypothesis that the species is a hybrid between a diploid parent and an allotetraploid parent is put forward.
authors.affiliation: Dipartimento di Biologia Cellulare e Ambientale, Sezione di Biologia Cellulare e Molecolare, Universita degli Studi di Perugia, via Elce di Sotto, 06123 Perugia, Italy. cionini@unipg.it
authors.forename: Marilena
authors.initials: M
authors.lastname: Ceccarelli
authors.forename: Vania
authors.initials: V
authors.lastname: Sarri
authors.forename: Stefania
authors.initials: S
authors.lastname: Minelli
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Gelati
mesh_terms: D001482:Base Composition; D001483:Base Sequence; D032461:Chromosomes, Plant / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics*; D004171:Diploidy; D006824:Hybridization, Genetic; D017404:In Situ Hybridization, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011123:Polyploidy; D031821:Potamogetonaceae / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D020080:Tandem Repeat Sequences
chemical_list: D018744:DNA, Plant